Just because Des Moines is not at risk for flooding does not mean it will not be affected, Des Moines Police Chief Roger Baker told council members on Oct. 29.

Water levels behind the Howard Hanson Dam are being kept lower after a depression was discovered in the right abutment. This raises the water levels of the Green River.

In a heavy rain, severe flooding is expected in parts of Tukwila, Renton, Kent and Auburn.

This will not be a one-time event, Baker said, and an estimated 25,000 to 40,000 people in the flood area may have to evacuated many times over.

The Army Corps of Engineers are working on interim measures to reduce the impact of the flooding, but a permanent solution could be a long ways out.

Work is being done on a concrete subterranean cutoff wall, but just planning and designing the wall is expected to take a year, and the Corps of Engineers has no idea how long it would take to build, considering the complexity of the problem.

The three primary evacuation routes out of Kent lead directly in Des Moines. Baker said that Des Moines currently has no plans to open a shelter, given available locations and staffing considerations.

There could be extended power outages in advance of and during flooding, when the power grid in the area is shut down to prevent damage.

There will also be disruption in distribution of goods from the valley, including fuel, food and building materials.

Directly affecting city staff and functions, some employees may not be able to get to work because they are in the flood zone, getting to work later because of traffic congestion or dealing with a loss of power at their house.

It is also likely city staff will be called upon to assist other cities with evacuations, traffic control or security controls. Baker said also the city may become a hub for resources forced to move off the valley floor.

Updates on Howard Hanson Dam can be found at http://www.nws.usace.army.mil.